Syringe with multiple plunger locks

Abstract

A syringe having a syringe body, a plunger, means to prevent the rear of the plunger from being gripped to retract the plunger when the plunger is at least at the fully forward position where all or most of the liquid has been ejected, and a catch on the plunger which prevents retraction of the plunger when the plunger is in at least the fully forward position.

1 . A syringe having:
 a syringe body having a forward end and an open rear end,   a plunger which is movable along the syringe body, the plunger having a plunger body, a plunger seal in a forward part of the plunger body, and a thumb pad in a rear part of the plunger body,   a needle holder which is in the forward end of the syringe body,   a needle which is attached to the needle holder, and,   a rear plunger lock which comprises at least one deflectable finger supported by the syringe body and which extends at least partially into the syringe body, the plunger having a catch in a forward part of the plunger, the catch engaging with the at least one deflectable finger when the plunger is sufficiently retracted, the catch and deflectable finger preventing the plunger from being fully retracted out of the syringe body.   
   
   
       2 . The syringe of  claim 1 , comprising at least two said deflectable fingers positioned in a rear part of the syringe barrel. 
   
   
       3 . The syringe of  claim 2 , wherein each deflectable finger comprises a cantilevered rectangular portion which is attached to the syringe barrel at a rear portion and is cantilevered towards the front portion of the syringe, and which has a length of between 3-20 mm and a width of between 3-10 mm. 
   
   
       4 . The syringe of  claim 2 , wherein the catch on the plunger comprises a collar which extends about the plunger such that the collar will catch against the deflectable finger irrespective of any rotation of the plunger relative to the barrel. 
   
   
       5 . The syringe of  claim 4 , wherein the collar is positioned close to and behind the plunger seal. 
   
   
       6 . The syringe of  claim 1 , wherein the needle can be retracted after use. 
   
   
       7 . The syringe of  claim 6 , wherein the needle holder is releasably held in the front of the syringe barrel and is biased to retract into the syringe body or the plunger, and a triggering means which is activated by the plunger and which allows retraction of the needle holder. 
   
   
       8 . The syringe of  claim 7  containing a second plunger lock mechanism which prevents retraction of the plunger when all, or substantially all of the liquid in the syringe has been expelled (zero mark position) but prior to triggering of the needle retraction mechanism. 
   
   
       9 . The syringe of  claim 8 , wherein the second plunger lock mechanism includes a catch in the rear part of the plunger, the catch adapted to engage with the at least one deflectable finger to prevent retraction of the plunger when the plunger is in the zero mark position. 
   
   
       10 . The syringe of  claim 9 , wherein the catch is a collar positioned in a rear portion of the plunger such that when the plunger is pushed forwardly, the collar passes underneath the at least one deflectable finger just prior to the zero mark position whereby the plunger cannot be retracted once the catch has passed the at least one deflectable finger. 
   
   
       11 . The syringe of  claim 1 , further including cover means to prevent the rear of the plunger from being gripped to retract the plunger when the plunger is at least at the fully forward position where all or most of the liquid has been ejected. 
   
   
       12 . The syringe of  claim 11 , wherein the cover means is a wall extending about a side portion of the end of the plunger when the plunger is pushed into the barrel, thereby preventing the rear of the plunger from being gripped to retract the plunger. 
   
   
       13 . The syringe of  claim 8  further including cover means to prevent the rear of the plunger from being gripped to retract the plunger when the plunger is at least at the fully forward position where all or most of the liquid has been ejected. 
   
   
       14 . The syringe of  claim 13 , wherein the cover means is a wall extending about a side portion of the end of the plunger when the plunger is pushed into the barrel, thereby preventing the rear of the plunger from being gripped to retract the plunger. 
   
   
       15 . The syringe of  claim 11 , comprising a further locking catch on the plunger which prevents retraction of the plunger when the plunger is in at least the fully forward position. 
   
   
       16 . A syringe having a syringe body, a plunger, means to prevent the rear of the plunger from being gripped to retract the plunger when the plunger is at least at the fully forward position where all or most of the liquid has been ejected, and a catch on the plunger which prevents retraction of the plunger when the plunger is in at least the fully forward position. 
   
   
       17 . A syringe having a syringe body, a plunger, and means to prevent the rear of the plunger from being gripped to retract the plunger when the plunger is at least at the fully forward position where all or most of the liquid has been ejected.